VOL. XVI. (3) DORSET AND HAMPSHIRE COASTS 271 
Beach, with the Corallian ridge terminating in The Nothe 
on the north side of the harbour, and the southerly- 
inclined Portland beds capping the steep bank on the 
south side of the harbour; and views of Portland Bill, 
where the Portland limestones have come down to sea- 
level, were sufficient to show that the Isle of Portland is 
composed of rocks belonging to the southern limb of this 
anticline. The Portland rocks have been extensively 
quarried on Portland, and the bottom-beds of the Purbeck 
—(with the celebrated Dirt-Bed, full of the silicified boles 
of trees)—have generally to be removed before the desired- 
for stone can be obtained. After seeing some excellent 
views of Lulworth Cove and the coast on each side, and 
Chapman’s Pool and St. Alban’s Head, the geological 
succession was picked up again at the Tilly Whim Caves, 
near Swanage, where the Portland Beds have been mined. 
The succeeding Purbeck Beds are well exposed along the 
coast between Durlston Head and Peveril Point. The 
well-known Purbeck Marble was formerly extensively 
worked near Swanage, but now few quarries are open, 
and the best place to obtain specimens is near Peveril 
Point. The soft Wealden Beds have been eaten into by 
the sea to form Swanage Bay, while at Punfield Cove we 
get the Punfield Beds. Views of Ballard Head, of the 
country visible from its summit, both towards Swanage 
and over Poole Harbour, were shown, while the Eocene 
beds were illustrated by views of the Bournemouth coast 
—both east and west of that famous watering-place. 
Mr Richardson concluded by saying that his main 
object in showing the views had been to try to impart 
some idea of the vast thickness of rock that must have 
once extended westwards towards the site of the Severn 
Valley. Not only had the Severn Valley been filled up 
